Process of making resister plates.



, A. s. sews. PROCESS OF MAKING REGISTER PLATES.

APPLICATION FILED APR-'22, 1 9M,

Patented Oct. 22 1918,.

2 SHEETS-SHEET I- INVENTOR.

AHTH 5. EIBMIS ITNESSES A. S. BEMISJ PROCESS OF MAKING RESISTER PLATES.

APPLICATIQN FILED APR-22.19I4.

Patented 001;. 22, 1918.

2 SHEETS-SHEET 2.

IN VEN TOR.

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WITNESSES:

STATES PATENT OFFICE.

ARTHUR S. 'ZBEHIS, OF CLEVELAND, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO

NATIONAL CARBON COMPANY IN 0.,

A CORPORATION OF NEW YORK.

rnocnss or MAKING nnsrsrnnrmrns.

To all whom it may concern: I

Be it known-that I, ARTHUR S. Bums, a citizen of the United States reslding at Cleveland, in the county of .duyahoga and State of Ohio, have invented a certain new and useful Improvement in Processes of Making Resister-Pla-tes, of which the followin is a full, clear, and-exact description.

This invention concerns. resisters adapted to withstand hi rapid disintegration by oxidatlon. Res1s ters of this kindare very largely required in electric furnaces of the resistance type and are very usefulin many other forms ofelectrical apparatus. However, the principal use of the resister. described. herein is in electric furnaces for meltinlg. metals and alloys, particularly brasses. or this purpose, carbon plates have been most account oftheir low conductivity and abilit to withstand high temperatures without meltirg or softening. Carbon plates are not satisfactory, however, when heated with free access of air at or. above a red heat.

When thus heated, they must be used in a reducing or indifferent atmosphere. To ob-' tain these conditions in ordinary furnace erally arranged in piles,

operation is usually inconvenient, difficult and expensive. In fact it is almost impossible in a commercial furnace to entirely exclude the oxygen of the air, and it therefore unites with the intensely heated carbon plates and causes them to be more or less rapidly consumed at the exposed surfaces.

The resister rings or plates, which are genare acted upon at the exposed edges and the combustion or disintegration of the carbon proceeds inward toward the center. The contact surfaces between the plates are but "ery little acted upon because they fit snugly and the air does not penetrate between the plates. It has therefore been proposed to coat the edges with some material which is not oxidized to any extent under the action of the air when highly heated. A number of non-oxidizable materials have been proposed for similar purposes, but the most with carbon resisters is probably carborundum, and the socalled carborundum fire sand" which consists of carborundum and compounds between silicon, carbon and oxygen.

y invention accordingly relates to an ad Specification of Letters Patent.

gh temperatures without widely used on satisfactory for use Patented Oct. 22, 1918.-

ate... filed April '22, 1914. Serial no. 833,638.

trid, etc. For convenience of expression, the

fire sand is hereafter referred to as carborundum.

In the drawings, modifications of apparatus suitable for carrying out the method Figure 1 shows a mold with partitions therein for making a single resister.

Fig. 2 shows a mold with partitions therein for makin simultaneously.

Fig. 3 is a plate for changing the depth of the mold.

Fig. 4 is a member for closing certain spaces formed by the partitio'is.

Fig. 5 shows the member of Fig. 4 placed in position in the mold.

Fig. 6 is an arrangement which may be substituted for the closing member of Fig. 4.

Fig. 7 is a modification of the device'of Fig. 4.

Fig. 8 illustrates a form of used with the 'mold of Fig. 1.

Flg. 9 shows the mold and plunger combined with the compression means.

Fig. 10 is a finished resister plate.

Fig. 11 is another filling device.

Protective coatings and edges have previously been applied by dip ing the portion to be coated or by forming t e resister and the coating separately. My invention, however, relates to a method which is applicable for use with the usual apparatus for molding carbon resistance plates and according to this invention, the protective coating or sheath and the resister are molded simultaneously.

In Fig. 1, I have shown a single mold for carrying out the process. This consists of a mold frame 1 having a cavity of the desired shape and size. In order to properly plunger to be 7 separate the mix for the resister portion of which illustrate severala plurality of resistersof thin metal istherefore, approximately twice the width of. the channel '4 because they form the prothree plates can be molded simultaneously.

enough material to form a plate of the 4 outside of the s acer. After the mixes are carefully leve ed up the spacer 2 is removed. A plunger that just fits inside the mold frame 1 is then forced into it against the mixes and the same are compressed to form a plate as shown in Fig. 10. I find that the pressure forces the two mixes together so that they cling firmly together and after the plates are baked, the protecting edge 25 and inside resister portions 24 are united together as if the entire plate were made of one mix. When a late made in this way is put in use, it is ound that the protecting edge does not crack off and the resister will last for an extended period even when heated as high as 1800 centigrade. The binder in the carborundum mix and that in the carbon mix, when the plate is baked, binds together the entire mass in a very effectual manner.

The process described above can be carried out b apparatus that will enable a plural it y Fig. 2, such a mold is shown in which It is, of course, understood that an number greater than this could likewise simultaneously molded.

Referring to Fig. 2 the mold body 1 consists of a block of metal havin a cavity out in its face of a depth suitab e to contain 8- sired thickness when compr The depth is made sufiicient to be adapted to the th1ckest desired resister late or block and difierentthickness may e obtained by inserting plates 3' (Fig. 3) of any desired thickness in the bottom of the mold. In the openin 3, a grid or separating frame of sheet meta is inserted. This frame consists of an outer band 6 uniformly spaced from and centered in the mold by means of the projecting lugs 5 to form an outer peripheral space 4, 4", 4 and 4. The distance between the mold and frame will depend upon the thickness of the protecting edge to be applied to the resister and this may be varied by using different sizeframes. If gnly one resister is to be made, as already described, no partitions are placed within the band 6, but if a plurality of plates are to be manufactured As shown in Fig. 1 these strips form five compartments, three of which, 8, 9 and 10 represent the spaces for the resistance material. The compartments 11 and 12,

between the compartments 8 and 9, and 9 and 10 respe tively, provide the space for the protective edges ofthe plates, and are tective edge for two adjacent plates. .When the molding piston compresses the mix in the mold two knives will at the same time 0 plates to be molded at the same time."

.ends, it would 'not be necessary plate back and forth in filling the mold,

cut or score these double edges 11 and 12 i0 the plates can be separated as is described ater.

It is a tedious task to fill the various compartments between the spacer and the mold and to facilitate this I use the device shown in Fig. 4. This device consists of three sheet metal or wooden blocks 13 held together by a member 14 and spaced 9. art to fit into the compartments 8,9 an 10 to the level of the top of the mold as shown in Fig. 5 so that excess material may be scra ed off in filling it. After the carborun um spaces are filled, device 13 is removed, and the carbon spaces are then filled with the mix and the same can be scraped level without substantially disturbing the filled carborundum spaces as the latter are relatively narrow. However if desired, the device shown in- Fig. 11 can be' used to cover th'ecarbornndum spaces while filling and levellin off the carbon spamces 8, 9 and 10. This evice is made of t sheet metal or other suitable material, and when it is fitted in between the pins 1, the turned. down ends 16, 16' abut against the sides of the. mold body. In this position the slots 23 line with the carbon compartments 8, 9 and 10 while the carborundum compartments are covered up. The carbon mix can now be filled and scraped ofi level without affecting the carborundum compartments.

' Fig. 8 shows a plunger 26 havin shaped separating member-27. The p on r isoperated by the hydraulic press 28 ig. 9 to com ress the mixes in the mold 1.

e late t us formed is scored or grooved sim taneously byemeans of the separators 27 so that it may readily broken at proper places to form three resister plates Instead of using the blocks 13 for closing certain openings, the sheet iron plate shown in Fig. 7 may be used. This plate has various openings in its surface that may be lined up with the compartments of the mold body. The distance between the turned down flanges 16' and 17 however, is greater than the width of the mold so that the plate can he slid either to the right or to the left of the mold shown in Fig. 2 with either the flan 16' or the flange 17 'abutting against t e corresponding end of the mold bod If the outside slots 19, 21 and 22 open intd each other at their ad'acent to sli e the ut this is imposible as the central part of the plate would-then not be connected to the outside art. It is, therefore, necessary to leave a t in ortion between the end of the slots refer to.

In using this plate to fill the carborundum compartments, it is fitted .in between the pins 1' of the mold body in Fig. 2 and slid to the ri ht until the flange 16 abuts against the left i and wallof the mold body 1. The carborundum mix is then placed on top of the plate to fill the compartments under the slots 19, 20 and 22. The surplus mix is then scraped off with a straight edge or similar tool. After this operation the compartment 4 is completely filled and leveled off, while the compartments 4, 11, 12 and 4 are filled and leveled with the exception of that portion of each beneath the webs 19, 19 19 and 19 respectively. The plate is then moved to the left of the mold body as shown in Fig. 2 until the flange 17 abuts against the right hand end of it. By placing the carborundum mix on the plate and scraping it off level, the compartment 1 under the slot 21 and the unfilled portions of the coinpartments 4, 11, 12 and 4", formerly under the webs 19 19*, 19 and 19 are filled and leveled off. The carborundum compartments are now entirely filled and leveled.

The carbon compartments can then be filled as previously described.

It will, of course, be understood'that it is immaterial whether the carborundum compartments are filled before filling the carbon compartments as the reverse process may be used. It is likewise immaterial in using the plate shown in Fig. 7 Whether it is first slid to the right until flange 16 abuts against the mold body or to the left until the flange 17 abuts against it, as it of course can be used either way.

It may be convenient to have the carbon and carborundum covers joined together in one plate and this is shown in Fig. 6. A handle 18 being there shown to manipulate the plate conveniently. By using the proper end of this plate, either the carbon compartments or the carborundum compartments can be filled in the same manner as previously described.

The mix used for the resister portion of the plate may consist of appropriate pulverulent material, and the carborundum or other protecting mix will be used in a pulverulent condition, either with or without a binder, depending on whether the same is necessary. The heavy pressure used to compress the two mixes causes them to be intimately united, and when they are baked a strong and permanent joint is established between the two materials. The line of union between the two is serrated or roughened slightly by the materials flowing slightly into each other when they are compressed which firmly secures them together. By this method the cracking ofl of the carborundum, which is the great disadvantage of other methods is minimized.

Although a plate made in accordance with the process just described is much superior to plates made by any process with which I am familiar, continuous use causes a slight disintegration of the outer surface of the carborundum. This, I think, is due to the slow disintegration of the binder which secures the carborundum particles togethcr. I find, however, that if the plates which are baked to a very high temperature, preferably under pressure in such a furnace as is described in the patent of John Brown, No. 1,198,616, granted Sept. 19, 1916, this slow disintegration of the carbon sheath is almost entirely eliminated. .I am not sure of the reason for this, but I think it is caused by the reaction between the carborundum fire sand and its carbon binder to form a chemical compound, probably carborundum, which is stable at fairly high temperatures in the presence of oxy en.

Although I have described my invention in reference to rectangular plates it will be evident that it is clearly adaptable to other forms such as segments and sectors of circles, sections of rings, and any other described form.

Having described my invention, what I claim'is:

l. The process of making a resisterbody which consists in filling a protecting material and a resistance material into temporarily separated compartments of a compartment mold, leveling all the material even with the top of the mold, removing the temporary separatingmeans, applying pressure to compact the materials, removing the compacted resisters from the mold and baking to a temperature suilicient to cause the materials to set together.

2. The process of making a resister bodv which consists in closing certain temporarily separated compartments of a compartment mold, filling the open compartments with a protecting material, leveling off the protecting material even with the top of the mold, removing the closing means and filling the remaining compartments with resistance material, removing the separating means from the mold'and applying pressure to compact and unite the materials.

In testimony whereof, I hereunto aflix my signature.

ARTHUR S. BEMIS. Witnesses:

S. H. FLEMING, H. G. GRovER. 

